In an electric power tool disclosed in Patent Document 1 below, a plurality of lock determination times to determine whether or not a motor has been locked and respective operation amounts of a trigger switch corresponding to the plurality of lock determination times are stored. More specifically, in a same speed mode, a larger operation amount is associated with a shorter lock determination time, while a smaller operation amount is associated with a longer lock determination time.
In the electric power tool, a control process described below is executed.
Specifically, an initial process is performed, and then it is determined whether or not the electric power tool is in an abnormal state. When it is determined that the electric power tool in a normal state, it is then determined whether or not the trigger switch is ON. When it is determined that the trigger switch is ON, a lock determination time corresponding to the operation amount of the trigger switch is selected, the motor is driven at a duty ratio corresponding to the operation amount of the trigger switch, and a counter for measuring an elapsed time required for the motor to rotate by a predetermined amount is incremented. If the motor has been rotated by the predetermined amount before a value of the counter reaches the selected lock determination time, the value of the counter is reset to zero, and a determination step regarding a battery voltage is performed, and then the aforementioned determination step regarding the abnormal state and subsequent steps are performed again. On the other hand, if the motor has been locked and the value of the counter reaches the selected lock determination time, it is determined that the motor has been locked, and the aforementioned determination step regarding the abnormal state is performed again, and it is determined that the electric power tool is in the abnormal state.